This invention relates to digital electroencephalograph (EEG) instruments or systems, and more particularly, to an EEG system including the provision of a visual display panel for indicating to an operator the particular pattern in which electrodes connected to the patient are being selectively processed to provide the desired signals.
Electroencephalographs that are in general use employ an analog signal generated by the brain for direct transmission to a recorder to obtain an appropriate readout of the signal. When the general procedure requires individual selection of pairs of electrodes or signal receiving terminals, the prior art units can be satisfactory. However in actual operating conditions, insufficient time is available to make such individual selections of the electrodes and therefore, electroencephalographs normally record a montage of wave forms comparing a series of selected electrodes and then switch to a different series of electrodes for recording comparisons of different electrodes. It is not unusual that up to ten such different runs comparing different sets of electrodes are recorded for a given patient. Thus, it is obvious that individual selections of different arrays of electrodes can require an excessive amount of time; and therefore, is impractical.
To overcome this problem, mechanical switches are in general use for selecting different montages of electrodes to couple to an associated output amplifier. These mechanical switches have preset stations by which the switch may select various combinations of electrodes for coupling and recording purposes.
In presently available EEG instruments there is no manner apparent on the operator control panel by which the operator may ascertain the actual montage of electrodes or the patterns in which the electrodes are being scanned to couple the signals to the output circuits. And, it is presently difficult if not impossible to correctly record the desired montage with absolute assurance of being correct in that selection.
The present invention overcomes this problem by providing a display console which visually provides the operator with a representation of the scanning pattern or montage. With this visual display, the operator can immediately confirm the pattern selection or scanning procedure being selected, at the time it is selected, thus providing a check on the internal wiring of the instrument.
Prior art electroencephalographs are normally analog signal devices, and have not fully utilized state of the art miniaturized electronic components and circuits and have remained bulky and relatively immobile. Increasing the capacity of prior art EEG instruments is difficult because of the increase in complexity, that is, the mass of extra wiring, connections, terminations, etc. to provide the corresponding desired increase in capacity of the instrument.
Accordingly, the present invention is premised on the important concept of providing an EEG system utilizing digital circuitry; and, the provision of display which is made feasible by converting the analog signal received from the electrode on a patient into a digital signal for processing. This analog to digital conversion not only makes possible a display panel, but also increases the capabilities of an electroencephalograph instrument. The conversion to a digital signal enables more efficient and less bulky state of the art electronics to be utilized, and also makes possible a direct connection to a data processor to gain the advantages of its comparative analytical abilities.
As mentioned above, the conversion to a digital signal allows the provision of an operator display panel to incorporate visual and mechanical features which were heretofore not commercially or practically possible. Through the use of a digital signal, a display of each and every electrode combination in use at a certain point in time can be effectuated for informing the operator of that particular combination.
Further advantages are found in the conversion to a digital signal in that it allows the expansion of the capability of the instrument without the corresponding increase in size and components. If it becomes desirable to expand the capabilities of a particular instrument by the addition of more additional electrodes, these electrodes may be added with the mere addition of a minimum of wiring and no increase in overall panel or instrument size. This decrease in size requirements for the instrument makes possible a truly portable instrument weighing approximately 25 to 30 pounds in contrast to the present sixty to seventy pound bulky instrument currently in general use.
Accordingly, it is a principal object of the present invention to provide a visual display panel to define, identify, and confirm the pattern in which the electrodes are electrically activated or scanned to provide a selected output.
It is another object of the present invention to convert the analog signal generated by the patient and transmitted by appropriate electrodes into a digital signal for use in an electroencephalograph instrument.
Still another object of the present invention is the use of digital signals to simplify the electronic circuitry of an electroencephalograph.
A further object of the subject invention is the reduction in size of an electroencephalograph to make it lightweight and portable and conveniently expandable in capacity without a corresponding increase in size by the use of digial components.
Further objects of the invention together with additional features contributing thereto and advantages accruing therefrom will be apparent from the following description of one embodiment of the invention when read in conjunction with the accompanying drawings wherein: